The present invention relates to a charged particle beam irradiation apparatus such as a scanning electron microscope, an X-ray micro-analyzer, and so on, and an irradiation method using the irradiation apparatus, and especially relates to an improved charged particle beam irradiation apparatus and an irradiation method using the irradiation apparatus, in which a display unit is used to designate a position on an image of a target area in a specimen, the target area being observed or analyzed by irradiation with a charged particle beam.
Scanning electron microscope, an X-ray micro-analyzer, etc., are known charged particle irradiation apparatuses. In a scanning electron microscope, a specimen is observed or inspected by using a magnified image of the specimen, which is formed by detecting secondary electrons or reflected electrons generated from the specimen irradiated with an electron beam. On the other hand, in an X-ray micro-analyzer, a specimen is examined by analyzing an X-ray emitted from the specimen irradiated with an electron beam. When a target area in a specimen, to be observed or analyzed by irradiation with a charged particle beam, is designated, a larger view of the specimen is displayed on an image display unit such as a CRT, an observation monitor, etc., by decreasing the magnification of the charged particle beam irradiation apparatus, and an image of the designated area in the specimen is moved near the central point on a viewscreen of the image display unit. Afterward, by gradually increasing the magnification, a view with the required magnification is obtained. However, since the magnified size of an inspected region in the specimen is smaller than the image resolution of the image display unit at the low magnification, the fine structure of the specimen is invisible, and it is difficult to find a point in the specimen to observe. Thus, an operator searches an inspected point in the displayed view by alternately repeating the specimen movement performed by operating a specimen fine movement device, and increasing the signification; or by moving the specimen fine movement device while observing the specimen with the magnification kept somewhat high.
Recently, there has been a stronger tendency for the inspection of a semiconductor memory to be performed with a scanning electron microscope in the fabrication processing of semiconductor memories. Usually in a semiconductor memory, a large number of cells with the same structure are arranged in an orderly latticework. Therefore, it is very difficult to quickly find a target cell on the viewscreen of a scanning electron microscope. when an operator searches a target cell in a specimen such as the above-mentioned semiconductor memory, the operator needs to memorize the row and column coordinates of the target cell in the specimen, and then find the target cell by counting the number of rows and columns in the latticework pattern by maintaining a somewhat high magnification such that the operator can discriminate each cell, and by gradually moving the specimen with a specimen fine movement device.
In a new type scanning electron microscope such that disclosed in Japanese Patent Application Laid-Open Hei 4-27908, if an operator designates any target position which s/he wants to observe in an image displayed on a viewscreen of an image display unit, a specimen fine movement device is automatically controlled by a motor so that the designated position is set at the central position of the viewscreen of the image display device. However, the operator needs to find the target position on the image of the specimen, which gives a comparatively heavy load on the operator.
The following method using the above new type scanning electron microscope has been devised as a measure to reduce the load of the operator having to designate a target position on the viewscreen of the image display unit. That is, in the new type scanning electron microscope, the first and second windows for displaying two images of the specimen, which are processed with high and low magnification respectively, are provided in the image display unit of this scanning electron microscope. Moreover, an area cursor is also displayed in the first window for the image processed with low magnification. Furthermore, it is possible to display the region inside the area cursor in the second window for high magnification. Thus, if the operator intends to observe a target cell at a position far from a terminal side position in a semiconductor memory, from which the searching of the target cell is started, the image of the specimen is displayed in the first window with a sufficiently decreased magnification, and the position where the target cell is located is enclosed in the area cursor. Further, the region enclosed in the area cursor is displayed in the second window with an appropriately increased magnification.
However, in the above-mentioned conventional scanning electron microscopes, if an operator searches for a position apart from one at a terminal side of a specimen by tens of columns or rows in an image formed with the magnification kept high to a extent such that the operator can discriminate the structure of a cell to be analyzed, the operator has to count the number of columns or rows from the terminal side to the position of the target cell. Also, in the scanning electron microscope with the ability to display images of the specimen at different magnifications, since an image of the target cell structure to be analyzed is too small on a viewscreen displaying a low-magnification image, it is difficult to count the number of columns or rows of cells. Even if the scanning electron microscope has the ability to automatically move the designated position of an image of the target cell in the specimen displayed on the viewscreen to the central position of the viewscreen, it is still necessary to count cells in the specimen while maintaining the magnification as high as necessary. Further, if the target cell is at a position far from a terminal side of the specimen by tens or hundreds of columns or rows of cells, since the target cell cannot be found with single specimen-movement operation, it is necessary to repeat the specimen-movement operation to find the target cell. The parallel execution of both the counting of the number of columns or rows and the repeating of the specimen-movement operation is likely to cause an error in the operator's counting of the number of columns or rows, for example, missing some columns or rows.